Liquid to gas converter



Nov. 29, 1966 c. D. FOX ETAL 3,288,207

LIQUID TO GAS CONVERTER Filed Feb. 10, 1964 5 Sheets-Sheet 1 J0 59 Nov. 29, 1966 Filed Feb. 10,

c. D. FOX ETAL 3,288,207

LIQUID TO GAS CONVERTER 1964 5 Sheets-Sheet 2 1 19 I F j] United States Patent 3,288,207 LIQUID T0 GAS CONVERTER Clarence D. Fox and John E. Lair, Decatur, Ill., assignors to Borg-Warner Corporation, Chicago, 111., a corporation of Illinois Filed Feb. 10, 1964, Ser. No. 343,797 11 Claims. (Cl. 16540) This invention relates to a converter adapted to change a liquid to a gas and in particular relates to a pressure regulator converter adapted to convert liquified petroleum gas under high pressure into a dry gaseous vapor at uniform temperature and low pressure for introduction into an internal combustion engine.

Liquid or liquified petroleum gas includes butane, propane and similar normally gaseous hydrocarbons, either in a pure state or in such mixtures as are commercially available. Because these fuels have vapor pressures up to approximately 250 pounds per square inch at normal temperatures they are highly volatile under atmospheric pressure, and cannot be effectively utilized unless they are stored under pressure in a liquid state. The liquid petroleum gas is normally carried in a closed tank on the vehicle such as a bus or truck which uses the liquified petroleum gas as a fuel. Since the tank is closed and since the vapor pressure of the petroleum gas is higher than atmospheric pressure, the tank is pressurized and the liquid is fed by conduit to the converter near the engine where it is converted into a gas by vaporization and partial release of pressure. In order to convert the liquid into a vapor it is necessary to supply heat because of the latent heat of vaporization of the fuel. The neces sary heat is supplied by a heat exchanger which may have its coolant supplied from the cooling water (approximate temperature range of 130 F. to 180 F.) from the engine coolant ssytem or may be some other coolant containing the necessary heat for the conversion from a liquid to a gas. Therefore the converter must vaporize the liquid fuel to a gaseous state at a given pressure for delivery to the engine and it must provide the necessary safety feature to prevent the escape of the highly volatile gas from the converter into the atmosphere in such quan tities sufiicient to cause an explosion.

It is therefore a general object of this invention to provide a liquid petroleum gas converter for converting liquid petroleum gas in a liquid state and under high pressure to a gas under a low pressure for delivery to the engine.

Another object of this invention is to provide a converter for dropping the fuel pressure from tank pressure to a low pressure, the converter having a pressure regulator that allows the fuel to be delivered in gaseous state at a pressure slightly above atmospheric pressure.

Another object of this invention is to provide a liquid petroleum converter unit having a built in pressure regulator, heat exchanger, and vapor control safety device.

Another object of this invention is to provide a fuel lock in the form of a manifold vacuum diaphragm operated solenoid valve as a safety device for the converter to prevent the escape of fuel vapor when the engine is not running.

It is also another object of this invention to provide for the converter a resiliently bias pressure regulator valve mechanism operative in conjunction with a pressure regulated resiliently biased diaphragm.

Another object of this invention is to provide cooling means for the converter fuel lock solenoid valve.

Still another object of this invention is to provide for a converter having manual priming means operating to charge the converter and vapor line to the engine carburetor under positive fuel pressure.

A further object. of this invention is to provide a converter with compensating adjusting means for the pressure regulating valve structure.

Another object of this invention is to provide a converter having an operating valve which operates against fuel pressure to permit fuel to enter the heat exchanger with a positive pressure.

Yet another object is to provide a single stage pressure reduction, complete, compact, liquid petroleum gas filtered regulating and vaporizing unit operating under pressure to provide improved operating characteristics of an internal combustion engine.

These and other objects and advantages of the invention will become apparent from the following description taken in connection with the accompanying drawings in which;

FIGURE 1 is a front view of the invention;

FIGURE 2 is a view taken along line 2-2 of FIG- URE 1;

FIGURE 3 is a URE 1;

FIGURE 4 is a sectional view taken along line 44 of FIGURE 3;

FIGURE 5 is a sectional view taken along line 55 of FIGURE 3; I

FIGURE 6 is a sectional view taken along line 66 of FIGURE 3;

FIGURE 7 is a sectional view taken along line 77 of FIGURE 5; v

FIGURE 8 is a sectional view taken along lines- 8 of FIGURE 7;

FIGURE 9 is a sectional view taken along line 77 of FIGURE 6;

FIGURE 10 is an enlarged sectional view of a portion of FIGURE 9; and

FIGURE 11 is a schematic view of the electrical circuitry of the safety fuel lock means.

Referring now to the drawings there is shown a liquid petroleum gas converter 10 for converting hydrocarbons such as butane or propane or mixtures thereof or the like from a liquid under pressure to a gas under a lower pressure. The converter 10 may have a fuel filter unit 11 such as shown in US. Patent No. 2,752,758 granted on July 3, 1956, to F. A. Tann. The inlet line 12 of filter coming from a fuel storage tank (not shown) and the outlet line 13 being coupled to threaded inlet 14 of the converter 10. i

The converter body 15 has a generally hollow interior and a general outer shell that is formed by a series of annular plate sections 16, 17, 18 and end covers or plates 19, 20 all held together by a series of bolts 21 and separated by gaskets 22. A fuel lock diaphragm structure 23 is held between the section 16 and cover plate 20 and defines with cover plate 20a manifold vacuum chamber 24. A pressure regulator or operating diaphragm structure 25 is held between sections 16 and 17 and defines with section or spacer 16 and the vacuum safety switch diaphragm structure 23' an atmosphere chamber 26. The section 17 defines with the main operating diaphragm structure 25 the positive pressure gas chamber 27.

The converter body 15 is mounted adjacent the carburetor of an internal combustion engine of the general type as shown in US. Patent No. 2,752,758 granted to F. Tann on July 3, 1956. The vacuum diaphragm cover plate 28 has a threaded bore 28 for receiving a conduit (not shown) for communicating with the intake manifold of the internal combustion engine. The inside of the cover plate 20 has a groove 29 communicating the bore 28 with the manifold vacuum chamber 24. The cover plate 20 has a counterbore 30a communicating with a push rod opening 30 receiving a stem portion or button view taken along line 33 of FIG- 31 of push rod 32. The vacuum diaphragm structure 23 comprises a round disc member 33 keyed by link pin 34 to an outer round flexible diaphragm 35 and having in the atmosphere chamber 26 annular grooved portion 36 on the pin 34 receiving the inner forked end 37 of lever 38 intermediately pivoted by pivot or roll pin 39 in cars 40, 40 of section or spring carrier 16. The other end 41 of the lever 38 is prevented from moving to the fuel lock diaphragm 35 by bar 39a attached to outer portions of the ears 40, 40. The other end 41 is forked to receive the stem portion 31 and is engageable with shoulder 42 of the push rod 32 formed between the outer button shaft portion 31 and the enlarged middle shaft portion 43 extending in aperture 44 in the section 16 (see FIGURES 2 and 6). The ears 40, 40 along with lugs 45 and 46 present a seat for conical spring 47 that diverges toward and engages with the disc 48 of operating diaphragm structure 25 held between sections 16 and 17. The disc 48 is connected by pin 49 to flexible dia phragm 50.

The push rod 32 has an inner shoulder 51 that is engageable with the under surface 52 of the section 16 and an inner shaft end portion 53 in aperture 54 of section 17 that engages button or stem 55 of electrical switch 56 mounted in cavity or opening 57 in the regulator section 17. This cavity 57 is open to the atmosphere at the bottom and communicates with the apertures 54, 44 and also communicates with opening 30 which communicates with the atmosphere. The switch 56 has two leads 59, 59 that go through opening 61 in plate 62 and are in electrical connection with leads 63, 63 of solenoid coil 71 and with the engine ignition switch I on associated instrument panel (not shown) and electrical power source (battery) B of circuit C. Manual operation of push rod 32 either by button 31 or suitable mechanical linkage 58 on the associated instrument panel operates switch 56 (see FIGURE 11). Plate 62 is held by bolts to section 17.

The solenoid mechanism 65 is contained within an open to atmosphere cavity 66 in section 17 and its leads 63, 63 also are in an aperture 67 in dielectric or terminal board 62 which covers the solenoid cavity 66 which communicates with hole 68 in section 17 which in turn communicates with hole 69 and slot 70 in section 16 which communicates with atmosphere chamber 26. The solenoid mechanism 65 comprises the electric coil 71 on spool 72 and leads 63, 63 and safety valve means 64. The spool 72 has aperture 73 through which extends tube 74 of the valve means 64. The end of tube 72 has a fiat plate 76 against it which plate 76 holds protective sleeve 77 around the coil by bolt 78. The upper portion 79 of the tube 74 has a threaded part 80 received in a bore 81 in the solenoid valve housing 82 of the section 17 and has a flange 83 with a gasket 85 against the top 86 of the cavity 66. The upper portion 79 also has a bore 87 that receives a lower valve plunger 88 containing in bore 88a a spring 89 urging the plunger 88 upward from the seat 90 in the bore 87. The upper end of the lower plunger 88 has a valve seat 91 of metallic disc 91a and elastomeric disc 91b engaging with the seat 92 the upper valve plunger 93 extending out of the cavity 87 of the tube 74. The upper plunger 93 has a lower annular groove 94 and a central longitudinally extending passage 95 extending therethrough and a valve end 96 of apertured metallic and elastomeric discs 96a, 961) on head 97 that engages with valve seat 100 of operating valve housing 102, the inlet 14 and passage 101 of the operating valve housing 102 being separated by the valve head 97.

The housing 102 has a passage 103 that joins passage 101 with the operating valve bore 104 in which is threaded operating valve member 105. The valve member 105 has a valve body 106 having a central bore 107 through which extends a plunger 108 having a stem 109 and a valve seat 110 of metallic and elastomeric discs 110a, 110b, the inner elastomeric disc engaging with seat 111 of valve body 106. The other end of the stem 109 has a cup 112 retaining spring 113 seated against seat 114 in end counterbore 115 of the valve body 106. Three orifices 116 spaced equally about the valve body 106 communicate the central bore or expansive chamber 1116!: with a passage 117 in the section 17. The passage 117 communicates with spiral heat exchange passage 118 in the heat exchange section 18 which has a wall 119 separating the passage 118 from water spiral passageway 120 connecting with the water inlet and outlet passages 121, 122. The heat exchange gas passages 118 communicate with port 123 communicating with the positive pressure gas chamber 27 in which is found the operating valve housing 102 and the solenoid valve housing 82. The stem tip 124 of the valve plunger 108 extends into the chamber 27, the tip 124 engaging the adjustable nylon bolt or screw 125 threaded in valve lever arm 126 of lever 127 pivoted on shaft 128 mounted on nub 128a in the operating valve chamber 27. The valve lever 127 which is generally L-shaped has a lower arm 129 with seat and guidepart 130 engaging and holding spring 131 held in threadably adjustable seat member 132 extending outwardly of the section 17 and having threaded thereon adjusting nut 133. The upper arm 126 of the valve lever 127 pivotally connects with one swivel ball joint 134 part of link 135 the other ball joint 136 of which connects with the arm 137 of generally L-shaped operating diaphragm lever 138 having an end pivotally connected by pin 139 to the chamber and another arm with an arcuate shaped end 141 engaging with button part 142 of pin 49 of operating diaphragm structure 25. The adjusting screw 125 is in line with the threaded gas outlet 143 of chamber 27 which outlet 143 is coupled with a conduit connected to the carburetor of the engine.

OPERATION The liquid petroleum gas is stored in the tank as a liquid but under a vapor pressure that may be as high as approximately 200 to 300 pounds per square inch (p.s.i.) and the liquid travels through the line 12, filter 11, line 13 and into fuel inlet 14 of the converter 10 v under pressures that may be as high as 200 to 300 psi.

and is blocked from entry into passage 101 by the solenoid operated valve means 64 of the safety fuel lock device.

The solenoid 71 may be operated by the manifold vacuum operated diaphragm 35 connected with the push rod 32 or manually operated either by suitable linkage 58 connected with the push rod 32, or by depressing the priming button 31 of the push rod 32. In all instances the push rod 32 operates the normally open circuit electrical switch 56 for energizing the solenoid 71 of the safety fuel lock circuit C. In the case of operation by the manifold vacuum operated diaphragm 35 the ignition switch I must be on or closing or completing the circuit C and the engine must be running or operating to develop a vacuum in the intake manifold. The manifold vacuum is connected with the diaphragm 35 through passages 28, 29 and allows the diaphragm 35 to move toward cover 20 because of the higher pressure in the atmosphere chamber 26. The lever 38 moved by the diaphragm 35 depresses push rod 32 inwardly operating electrical switch 56 which complete electrical circuit C and solenoid coil 71 then operates on solenoid operated valve means 64 through the magnetic lines of force developed about the coil 71 and valve means 64 to move the valve means 64 to an open position against the action of spring 89 allowing the liquid (which may have some vapor in it) to enter passage 101. When the engine is not'nlnning and the ignition switch 56 is in the closed circuit position, the push rod 32 in the absence of manifold vacuum is not held by diaphragm 35 and switch 56 opens circuit C. Manual depression then of button 31 allows the button to contact the electrical switch 56 to energize the solenoid 71 and open the valve means 64 in the closed circuit position of the ignition switch I as does manipulation of the control linkage 58 on the instrument panel. The solenoid 71 in use becomes heated and is cooled by the vibration of the operating diaphragm 50 sending fluctuating air waves under pulsating pressure from the atmospheric chamber 26 by way of passages 68, 69, 70 to the cavity 66 surrounding the solenoid 71. Thus it is seen fuel fumes cannot escape from the converter when the ignition switch I is in the closed circuit position and the engine has stalled or stopped and is not developing a manifold vacuum. If the engine is stalled the fuel lock diaphragm 35 not being subject to manifold vacuum will return to rest position moving lever 38 moving push rod 32 away from the electrical switch 56 which will move to an open circuit position under its own bias and allow the solenoid operated valve means 64 to seat under influence of its spring 89.

The solenoid valve means 64 comprises the upper and lower plungers 88, 93 which under normal operating condition will move together away from seat 97 under influence of the solenoid 71. Should excessive fuel pressure relative to pressure in passage 101 tend to keep the valve means 64 seated the lower plunger 88 will move away from the upper plunger 93 under the influence of the solenoid 71 and becomes a pole face. Some fuel under pressure is then allowed to escape through passage 95 in the upper valve plunger 93 whereby solenoid 71 can then cause the upper plunger 93 to move away from the seat 97 to fully open the valve means 64.

With the solenoid valve means 64 in the open position the liquid fuel is allowed to enter to passages 101 and 103. The pressure regulating valve structure 105 in the open position allows the liquid fuel to enter past the valve seat into the valve expansion chamber 116a where the fuel is allowed to expand to a gaseous stage entering the passages 116, 117 and heat exchange passage 118. The expansion of the fuel from a liquid to a gas results in a cooling effect and the heated engine water in water passages 120 supplies the necessary heat of vaporization to prevent freezing and icing of the converter 10. The gas passes from passage 118 through opening 123 into the positive pressure chamber 27 to outlet passage 143 for communication with the associated engine carburetor.

It is thus seen that the fuel is a liquid in passage 103 under several hundred p.s.i. but the fuel is a gas under positive pressure (i.e. pressure above atmospheric pressure and above engine manifold pressure) which is only a fraction of above atmospheric pressure say in the order of .05 to 0.10 p.s.i. above atmospheric pressure. The conical compression spring 47 in the atmosphere chamber 26 is of such a rate or load as to maintain this slightly positive pressure in operating chamber 27. The spring 47 exerts a force on the diaphragm 50 moving diaphragm 50 inwardly into chamber 27 moving diaphragm lever 140 counterclockwise into chamber 27 about pin 139 as viewed in FIGURE 7 to cause link 135 to move to left as viewed in FIGURE 5 pivoting valve lever 127 counterclockwise about pin 128 as viewed in FIGURE 5 resulting in compression of spring 131 and movement of adjusting screw to left (FIGURE 5) against stem tip 124 to move valve stem 108 to left (FIGURE 9) against spring 113 to move valve seat 110 away from housing end 106a opening valve means 105 against the high pressure exerted against valve seat 110 in passage 103. When the valve means 105 is so opened it is at a rest position. As the pressure builds up in chamber 27 the movement of the valve means 105 is reversed to a closed position by pressure exerted on the operating diaphragm 50 moving the lever 140, rod 135 and valve lever 127 in the reverse direction with the aid of the adjustable spring 131. The desired positive pressure in the chamber 27 may be determined by adjustment of spring 131 and by the rate of the conical spring 47 used. The opening of the valve means 105 against positive pressure leaves the operation of the valve means 105 generally unaffected by any rapid fuel velocity changes in the liquid fuel lines leading to the valve means 105.

The diaphragm 27 during operation pulsates at a high or fast frequency so that wear is placed on the lever 127, rod and linkage and their respective pivots. The adjustment screw 125 may be positioned so as to compensate for any pressure irregularity due to the wearing of these parts.

Thus it is seen that the converter 10 comprises a single stage pressure reduction chamber 27 controlled by an adjustable pressure regulator or expansion valve structure 105, 125, 127, 131, 135, 138 regulated by a biased pressure responsive diaphragm structure 25, 47 whereby there is provided a phase transfer of the fuel from a liquid under high pressure to a dry vapor under low pressure which is preferably slightly greater than atmospheric pressure with a hot water heat exchanger 18 supplying the necessary latent heat of evaporization and with the provision of safety lock means to prevent the escape of vapor in the form of a manifold vacuum operated diaphragm structure 23 or manually operated means 31, 32 acting on a safety switch 56 which actuates a solenoid or electromagnetic operated valve means 64, 71 and wherein the solenoid 71 is housed in the cavity 66 of the converter unit 10 and cooled by pulsations of the pressure regulator diaphragm 50. In some instances the vapor pressure in pressure reduction chamber 27 may be below atmospheric pressure but above engine intake manifold pressure and the vapor pressure may even be below engine intake manifold pressure depending on the setting of the pressure regulator valve structure, the term positive pressure being taken to be above atmospheric pressure or at least of intake manifold pressure so that the vapor pressure can flow out of the pressure reduction chamber 27 to the engine carburetor.

The reference in the specification to specific pressure values or geometric orientation terms such as top or bottom, etc. are given here by way of example and illustration and not as limitatiton on the scope of invention.

The particular embodiment of the invention has been described and illustrated, it is apparent that modifications and alternations may be made thereon. It is therefore the intention in the appended claims to cover all subject modifications and alterations as may fall within the true spirit and scope of the invention.

What is claimed is:

1. A liquid petroleum gas converter comprising; a.

between, a mechanically operable normally open elec-.

trical switch disposed within said housing and adapted to be connected in series between said solenoid operated valve and a source of power, operation thereof being effective to move said solenoid operated valve from said closed position to said open position, and means associated with said switch to effect operation thereof, said means including means responsive to a pressure signal from an intake manifold of an internal combustion engine.

2. A liquid petroleum gas converter as claimed in claim 1 wherein said means responsive to a pressure signal from an intake manifold of an internal combustion engine includes a chamber defined by said converter housing and by a diaphragm movable in response to changes in the pressure signal, said chamber being adapted to be connected to a source of engine intake manifold pressure, and linkage interposed between said diaphram and said switch effective to operate said switch in response to movement of said diaphram.

3. A liquid petroleum gas converter as claimed in claim 2 wherein said means associated with said switch to efiect operation thereof additionally includes a manually operable means engageable with said switch and extending outwardly of said housing, movement of said means in a direction toward said switch being effective to close said switch.

4. A liquid petroleum gas converter as claimed in claim 1 wherein said housing further defines a heat ex-' changer interposed between said vapor expansion chamber and said vapor outlet, said heat exchanger including a vapor passage in communication with said vapor expansion chamber and said vapor outlet and additionally includes a heat exchange fluid passage adapted to allow circulation of a heat exchange fluid therethrough to effect heating of said vapor in said vapor passage.

5. A liquid petroleum gas converter as claimed in claim 1 wherein said housing further defines a positive pressure chamber interposed between said vapor expansion chamber and said vapor outlet, said positive pressure chamber including a vapor pressure responsive diaphram movable in response to variations in said vapor pressure in said positive pressure chamber, and wherein said means adapted to control the rate of flow into said vapor expansion chamber includes a valve member interposed between said liquid inlet and said vapor expansion chamber and having a closed position preventing flow from said inlet to said vapor expansion chamber and an open position allowing flow therebetween, and motion transmitting linkage disposed in said positive pressure chamber engaging said diaphram of said chamber and said valve member to transmit movement of said diaphram to said valve member to move said valve member between said closed and said open positions.

6. A liquid petroleum gas converter as claimed in claim 5 wherein said motion transmitting linkage includes adjustable means engageable with the valve member to compensate for wear of said linkage.

7. A liquid petroleum gas converter as claimed in claim 6 wherein said housing further defines a heat ex; changer interposed between said vapor expansion chamber and said vapor outlet, said heat exchanger including a vapor passage in communication with said vapor expansion chamber and said vapor outlet and additionally includes a heat exchange fluid passage adapted to allow circulation of a heat exchange fluid therethrough to eifect heating of said vapor in said vapor passage.

8. A liquid petroleum gas converter as claimed in claim 5 wherein said housing further defines with said diaphram of said positive pressure chamber an open to atmosphere chamber, said atmosphere chamber communicates with said solenoid operated valve, and movement of said diaphram of said positive pressure chamber effects movement of air from said atmosphere chamber to said solenoid operated valve to cool said solenoid operated valve.

9. A liquid petroleum gas converter as claimed in claim 5 wherein first spring means engages said diaphram of said positive pressure chamber and urges said diaphram into engagement with said linkage interposed between said diaphram and said valve member urging said linkage in a direction away from said valve member, second spring means urges said linkage into engagement with said diaphram, and third spring means associated with said valve member biases said valve member toward said'closed position and in a direction toward said linkage.

10. A liquid petroleum gas converter as claimed in claim 9 wherein said linkage interposed between said diaphragm of said positive pressure chamber and said valve member includes adjusting means engaging said valve member and controlling the rate of force of the first and second spring means and the vapor pressure in the positive pressure chamber.

11. A safety lock device for a liquid to gas fuel converter having a housing defining a vapor expansion chamber and a positive pressure chamber, said converter including a gas pressure regulating valve, and a liquid inlet valve communicating with pressure regulating valve and having an opened and closed position, a solenoid means operatively connecting said valve, and means connecting with and energizing said solenoid means for moving said valve from said closed to said opened position, and means for cooling said solenoid means comprising an atmosphere chamberdefined by said housing and a pressure regulator diaphragm interposed between said atmosphere chamber and said positive pressure chamber, said diaphragm being movable in response to variations in vapor pressure in said positive pressure chamber, and said housing defining a passage from said atmosphere chamber to said solenoid chamber, movement of said diaphragm effecting delivery of air to said solenoid means through said passage.

References Cited by the Examiner UNITED STATES PATENTS 2,248,222 7/1941 Ensign 4O 2,272,341 I 2/1942 Holzapfel 16540 2,752,758 7/1956 Tann 16551 ROBERT A. OLEARY, Primary Examiner.

CHARLES SUKALO, Examiner. 

1. A LIQUID PETROLEUM GAS CONVERTER COMPRISING: A HOUSING HAVING A LIQUID INLET AND A VAPOR OUTLET AND DEFINING A VAPOR EXPANSION CHAMBER INTERPOSED THEREBETWEEN, MEANS INTERPOSED BETWEEN SAID LIQUID INLET AND SAID VAPOR EXPANSION CHAMBER ADAPTED TO CONTROL THE RATE OF FLOW INTO SAID VAPOR EXPANSION CHAMBER, A SOLENOID OPERATED VALVE INTERPOSED BETWEEN SAID MEANS CONTROLLING THE FLOW INTO SAID VAPOR EXPANSION CHAMBER AND SAID LIQUID INLET, SAID SOLENOID OPERATED VALVE BEING MOVABLE BETWEEN A CLOSED POSITION PREVENTING FLOW FROM SAID INLET TO SAID MEANS AND AN OPEN POSITION ALLOWING FLOW THEREBETWEEN, A MECHANICALLY OPERABLE NORMALLY OPEN ELECTRICAL SWITCH DISPOSED WITHIN SAID HOUSING AND ADAPTED TO BE CONNECTED IN SERIES BETWEEN SAID SOLENOID OPERATED VALVE AND A SOURCE OF POWER, OPERATION THEREOF BEING EFFECTIVE TO MOVE SAID SOLENOID OPERATED VALVE FROM SAID CLOSED POSITION TO SAID OPEN POSITION, AND MEANS ASSOCIATED WITH SAID SWITCH TO EFFECT OPERATION THEREOF, SAID MEANS INCLUDING MEANS RESPONSIVE TO A PRESSURE SIGNAL FROM AN INTAKE MANIFOLD OF AN INTERNAL COMBUSTION ENGINE. 